1. Field of the Invention
This invention relates to lighting arrangements utilizing a three-dimensional electro-luminescent lighting element, and to a three-dimensional electro-luminescent lighting element for use in such lighting arrangements.
2. Discussion of Related Art
The advantages of using electro-luminescent lighting elements in a variety of contexts are explained in several copending U.S. patent applications and issued patents of the Inventor. Serial numbers of the copending U.S. patent applications include Ser. Nos. 08/305,294; 08/343,404; 08/343,915; 08/383,404; 08/383,405; 08/409,925; 08/421,647; 08/432,707; 08/438,373; 08/444,064; 08/436,007; 08/444,064; 08/489,160; 08/498,258; 08/510,701; 08/522,940; 08/561,973; 08/611,049; 08/614,001; 08/522,940; 08/712,484; and 08/734,872, and the issued U.S. Pat. Nos. include 5,451,842; 5,469,342; 5,475,574; 5,479,325; 5,566,384, 5,570,946; 5,572,294 and 5,734,336.
The super-thin lighting arrangements described in the above-cited patent applications and patents of the Inventor are generally made up of multiple layers, including a protective backing layer, a conductive layer which forms an electrode, at least one phosphor layer, another conductive layer forming the second electrode, and a transparent protective layer, to form a strip or panel which emits light through either one or both of the protective layers, depending on the number of phosphor layers and the arrangement of the conductive layers. This type of electro-luminescent strip is thinner and more flexible than conventional lighting elements, and as a result is beginning to enjoy widespread popularity for a wide variety of applications.
One commercially available example of such an electro-luminescent strip or panel arrangement is manufactured by Durel Company USA, whose electro-luminescent panels are used in Timex Corporation's INDIGLOO.TM. watch. The Durel Company electro-luminescent panel is a multi-layer type panel made up of a conductive layer, a dielectric layer, a phosphor layer, and filter layers with micro-encapsulated particles to obtain a thickness of between 0.2 mm and 0.4 mm, and is used to provide background illumination in wristwatches and wall clocks, making use of the large area illumination and low power consumption of the panels.
Despite their advantages, however, the Inventor has discovered that flat electro-luminescent panels of the type discussed above have a number of limitations, which have not been previously appreciated. The main limitation is that the light can only be emitted in a single direction, meaning that to provide backlighting over a large area such as the face of a clock, the panel must extend over substantially the entire area as in the Timex watch, or the panel must somehow be bent so that light from the panel is emitted in an additional direction to illuminate the face of the clock.
While the relative thinness and flexibility of the conventional electro-luminescent panel would appear to permit bending of the panel into a relatively small-diameter cylinder, which would permit light to be emitted over larger angles, in practice the minimum bending radii of the panels, i.e., the smallest bending radius to which the panel can be bent without damaging any of the interior layers of the panel and causing dark spots to appear, is still too large to permit formation of cylindrical lighting elements with sufficient transverse flexibility to make them suitable for use in most applications.
For example, the minimum bending radius for a typical flat panel having a thickness of 0.28 mm is approximately 8.0 mm, and thus to form a cylinder having a length of ymm and a diameter of 16 mm would require a panel of (16.pi..times.y)mm.sup.2. Such a panel would be both too large for use on a watch, and for most other applications requiring 360.degree. illumination, such as lace illumination arrangements, and yet would require an excessive size of flat panel for the coverage provided by the three-dimensional illumination. As a result, three-dimensional electro-luminescent arrangements made by simply bending a flat electro-luminescent panel are impractical.
In addition, conventional electro-luminescent panels are provided with fixed output terminals which generally must be situated at the edge of the panel, severely restricting choice of panel placement applications which can accommodate the necessary wiring. This is particularly inconvenient for custom designs or do-it-yourself applications, in which it would be advantageous for the consumer to make the terminals rather than having to work around fixed terminals.
Added to the physical limitations of conventional flat panel-type electro-luminescent lighting arrangements are the limitation of offering only a single color per phosphor coating, with multiple coatings needed to provide multi-color effects or to provide two-sided illumination.